The index of a directory can come from one of two sources: * A file written
by the user, typically called index.html. The
DirectoryIndex directive sets the name of this file. This is controlled
by mod_dir.
* Otherwise, a listing generated by the server. This is provided by
mod_autoindex.
The two functions are separated so that you can completely remove (or replace)
automatic index generation should you want to.
A "trailing slash" redirect is issued when the server receives a
request for a URL http://servername/foo/dirname where dirname is
a directory. Directories require a trailing slash, so mod_dir issues a
redirect to http://servername/foo/dirname/.